Probably my favourite of season 11. We get all the unit regulars, car/boat chases, and giant spiders. Yates gets his redemption, there is another time lord who regenerates, which of course also happens to the Doctor as he is drained with usage of the blue crystal  and from his battle with the Great One. Pertwee is my favourite classic Doctor, so it's sad to see him go, but season 11 probably was his weakest and it's always exciting to see the next Doctor.